[PATCH 2/2] UML - Speed up exec

[Jeff Dike <jdike@addtoit.com>]

flush_thread doesn't need to do a full page table walk in order to
clear the address space.  It knows what the end result needs to be, so
it can call unmap directly.

This results in a 10-20% speedup in an exec from bash.

Signed-off-by: Jeff Dike <jdike@linux.intel.com>
--
 arch/um/kernel/skas/exec.c |   12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

Index: linux-2.6.21-mm/arch/um/kernel/skas/exec.c
===================================================================
--- linux-2.6.21-mm.orig/arch/um/kernel/skas/exec.c	2007-03-30 10:28:24.000000000 -0400
+++ linux-2.6.21-mm/arch/um/kernel/skas/exec.c	2007-03-30 10:30:15.000000000 -0400
@@ -17,7 +17,17 @@
 
 void flush_thread_skas(void)
 {
-	force_flush_all();
+	void *data = NULL;
+	unsigned long end = proc_mm ? task_size : CONFIG_STUB_START;
+	int ret;
+
+	ret = unmap(&current->mm->context.skas.id, 0, end, 1, &data);
+	if(ret){
+		printk("flush_thread_skas - clearing address space failed, "
+		       "err = %d\n", ret);
+		force_sig(SIGKILL, current);
+	}
+
 	switch_mm_skas(&current->mm->context.skas.id);
 }